Odorant for gaseous fuels



Patented Sept. 28, 1937 UNiTE cream ODOR/ANT FOR GASEOUS FUELS William H. Hampton and John T. Rutherford, Berkeley, Calif., assignors to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware No Drawing. Original application December 17,

1929, Serial No. 414,817. Divided and this application August 16, 1932, Serial No. 629,050

12 Claims.

This invention relates to an odorant for gaseous fuels, and more particularly refers to a volatile compound for use as an odorantfor natural gas and other heating and illuminating gas, and includes certain vaporized and gaseous products resulting from liquid or liquefied petroleum fractions. More particularly, the invention relates to a novel odorant produced from what has heretofore been considered a Waste product, namely, acid sludge, which results from the treatment of petroleum oils with sulphuric acid.

This application is a division of our cb-pending application, Serial No. 414,817, filed December 17, 1929 and which has issued into Patent 2,064,805, December 15, 1936.

Ordinarily, natural gas and other fuel gases do not, of themselves, possess sulficient odor to Warn of their presence when they escape from the containers, piping, or fixtures wherein they are used; and a danger results in such instances due to the explosive or toxic hazards created.

Natural gas, such for example as is obtained from natural gas wells and oil wells, does not possess a marked odor. Consequently, when natural gas is used for heating, cooking or illumination in the home or in industrial plants, it is possible for asphyxiative or explosible quantities of the gas to accumulate unnoticed by the persons in contact with the gas.

Various odorants have been used heretofore to give the gas a characteristic odor which will give proper warning of danger. So far as is known, all colorants heretofore employed have one or more objections. Some odorants are not distinctive and do not rouse the victim to action, or

the odorant, while distinctive, may be so offensive that users of the gas containing the odorant object to the odor. With some odorants, exces sive quantities of odorant are required.

The odorant which is the subject of the present invention has a distinct and penetrative odor. It is easily and unmistakably detectable before explosive mixtures or asphyxiative concentrations are reached. In addition merely of warning one of its presence, it is sufiiciently distinctive to rouse one to action. On the other hand, it is not so obnoxious as to be objectionable to the customer.

When used in proper proportions, the odorant embraced by this invention does not produce any undesirable physiological action, such as skin irritation, ,lacrimation, or the like. Furthermore, the products of combustion are substantially odorless when used in the proportions necessary to impart distinct warning characteristics to the gas.

In this novel odorant there exists a series of. volatile organic compounds. While most of these are believed to be principally organic sulfides of 5 the saturated ring heterocyclic type, containing three or more carbon atoms and sulfur as a hetero-atom, other organic sulphur compounds, such as aliphatic sulfides, disulfides, polysulfides, mercaptans and thiophene homologues, may be incidentally present. The saturated ring heterocyclic sulfides referred to are to be distinguished from hydrosulfides or mercaptans (R-S-H type) and from thiophenes which contain only four carbon atoms and are unsaturated. They have an odor which is distinct from the odor of common mercaptans and from thiophenes, and. principally comprise the effective odorizing constituents of the odorant oil herein described. Their odor is readily distin uished from the mild odor of the thiophenes, it being remembered that disulfides have practically no odor and are of no importance in the performance of this invention. There may also be present non-sulphur bodies. Some of these sulphur compounds are of the type such that they have a distinctive, intense and penetrative odor, so that minute quantities can be used to impart the necessary odor to the gas. The quantities required are so small that the sulphur content of the gas is not appreciably increased over that which ordinarily exists in the gas.

The odorant embraced by this invention is distinctly perceptible by most people when it exists at a concentration of 9.25 part per million. In other words, when the product is used in the proportion of three gallons per million cubic feet of gas, it willproduce a distinct odor when liberated in a room when a sumcient quantity of the gas is admitted into the room so that 0.5 percent of the odorized. gas is present in the air thereof. These sulphur compounds occur in many petroleum oils, so that when such oils are treated with suitable re-agents, such as sulphuric acid, they will be found to exist in the resulting acid sludge. This sludge may be distilled, or it may first be subjected to hydrolysis and then distilled to produce a volatile component in which these sulphur compounds will be found.

The sulphuric acid may react on certain of the compounds normally existing in oil so as to change them in molecular structure during the recovery process.

The properties of the odorant may vary considerably and may depend upon the type of sludge 2 from which it is obtained and the volatile portion of the sludge oil selected as the odorant. The

variation in the physical and chemical properties of the odorant is shown by the following inspections on five different odorants, any one of which or any combination of which will produce a suitable odorant. I 7

white to yellow or amber, but is usually yellow. ;While the properties of the odorants listed above vary considerably, it is possible to control the process of production so aszto obtain a uniform odorant'havin g any desired properties. We

find that the sulphur content of our odorantmay range from 2% to 30%, bywe ight, of the odorant, but usually does not exceed 18%. 1

The boiling point range of the odorant may range between 100 F. and 600 F. The selection of a suitable boiling point range for any specific odorant will depend upon two factors; first, the amount of odorant required to impart a noticeable odor to the gas; and, second, the temperature and pressure under which the gas is storedv and distributed. It is essential that odorant should evaporate completely and the distillation of the sludge should be carried outwith this in mind. Since gas is distributed under varying pressures and temperatures an odorant must be selected which will evaporate under the highest pressure and lowest temperature existing in the distributing system. We find, for example, that where gas is distributed at pressures as high as 250 pounds per square inch and at temperatures as low as 55 F., the odorant should have an end point not over 420 F,, and should yield 70% by distillation at 340 F. With lower pressures and higher temperatures, odorants having'higher boiling points can be used. Likewise, for higher pressures and lower temperatures the odorant should have lower boiling points. 7 V The concentration of odorant required in the gas to produce the distinct and penetrating odor desired is an important factor in the selection of an odorant. An odorant made from sludge resulting from the acid treatment of raw cracked gasoline or straight run gasoline is particularly desirable onaccount oi the low concentrationsrequired to produ-cea satisfactory odor. V

Itshould be noted, however, that the method of treating may also influence the character of; the odorant. Thus, two sludges produced from the same oil stock but with different acid-treatments, such as with various'kinds, amounts or strengths of acid at different temperatures, will have. different physical properties. The lighter petroleum oils, such'as naphthas, gasoline,.and

kerosene, are the best source of volatile organic sulphur compounds, although small amountsof Mixtigedof Mixttll zredoi Straight crac e crac e Cracked gasoline gasoline Type of Sludge gasoline gg Kerosene .kerosene, kerosene, liquid .petliquid petrolatum rolatum Odorant Gravity, A. P. I 30. 8 26. 6 27. 25. 7 3. 0 Percent sulfur-" 9. 18% 15.48% 2.13% 4. 68% 5. 09 Color Saybolt Below-'9 Below-9 Below9 Below9 Below-9 Flash, closed Tag" Below 80 80+ 100+ 124 F. Below-8O A. S. T. M. dist. range 7 Temperature, degrees Fahrenheit Start 160 F. 252 F. 300 310 F. 112 F; 20 percent. 284 312 352 372 229 Percent distilled 50 percent. 349 335 372 406. 302' V 90 percent 490 386 430 466 361 End point 495 432 w 453, r V 524 390 The color of the. odorant ranges from water late to different methods of obtaining the odorant from the sludge and are given to enable those skilled in the art to produce the odorant.

Petroleum oils are usually treated with acids for removal of impurities. Among the impurities which it is desirable to remove are the organic sulphur compounds. These are commonly removed by the'use 'offlsuch' acids as sulphuric acid, including fuming sulphuric acid, sulphuric anhydride ($03), or sulphur dioxide. The organic sulphur compounds are composed mainly of organic sulfides, disulfides, polysulfides, mercaptans and thiophene homologues.

During the acid treatment, these organic sulphur compounds are dissolved in or combined 'with the acid. In either event, they will be found in the sludge resulting from the acid treatment. a

The odorant which is the subject of this invention can be'obtained, containing these organic sulfides, by distilling the sludge by any of the well-known methods, either at atmospheric or superatmospheric pressure or with vacuum, and condensing the volatilized constituents resulting from the distillation. The condensate formed is a an oily compound. A part of the acid component of the sludge is distilled over with the sulphur compoundsand a part is reduced to sulphur dioxide, both of which are recovered from the condenser, some of the S02 will be dissolved in the water formed during the distillation, while most of the S02 will pass off as a gas. The acid distillate readily separates. from the oily compound in the condensen The oily compound is withdrawn separately and may be further puri fied, if necessary, by' neutralizing and washing with water. The neutralization may be desirable so as to remove any sulphur dioxide or acid which may be present, thereby preventing any corrosion in the gas lines or containers. The resulting finished product which is the odorant, is passed to storage. If desired, the volatile oil vapors may be condensed by means of a fractional eondenser.

Although'the desired odorant can be obtained by simple distillation of some sludges, it is preferred; with most sludges, such as the" sulphuric acid sludges, to first hydrolyze the sludge to produce a weak acid and a tar, the odorant being recovered from the tar by distillation. The usual method of recovery is to add water to the'sludge,

causing it to hydrolyze into weak sulphuric acid and an organic remainder sometimes called a tar. Some sludges are readily hydrolyzed at normal temperatures, whereas others require heating. Some sludges require heating at temperatures above their boiling point, thus necessitating the use of pressure above atmospheric in order to reach the high hydrolyzing temperature. The acid and tar separate into two layers and may be recovered separately. The upper or tar layer contains the odorant.

If the tar from which the odorant is to be obtained has been produced by hydrolyzation of sludge at normal temperatures, that is, without the application of heat to the hydrolyzing chamber, it is necessary to distill the tar and recover those fractions which are distilled off at temperatures up to about 600 F., and which are condensable at atmospheric pressures. Any of the conventional distilling apparatus may be employed. A fractional condenser may be used to collect and separate any desired portion of the vapors.

If the tar from which the odorant is to be obtained has been produced by steaming or heating in an open tank, a more volatile odorant will be produced. If it is desired to lower the volatility of the odorant, this can be accomplished by distilling and fractionally condensing such portions of the vapors as are desired for the odorant.

If the tar from which the odorant is to be obtained has been produced by hydrolysis at high temperatures and super-atmospheric pressures, the volatile fractions of the tar can be obtained by passing the tar from the sludge digester, through a pressure regulating valve, into an evaporating chamber. The volatile portions of the tar containing the odorant may be vaporized by the residual heat in the tar and may be withdrawn from the chamber and condensed. Inasmuch as the volatile tar vapors from the evaporator are usually accompanied by some sulphur dioxide vapors, it is desirable to separate them from each other. Since sulphur dioxide gas is readily soluble in water, a separation can be obtained by passing all of the vapors from the vaporizing chamber through a body of water or through a scrubbing tower. One convenient method of separating the vapors is to remove them from the vapor chamber by means of a jet condenser, using water as the condensing medium. The sulphur dioxide gas is dissolved in the water and the less volatile oil vapors are condensed. The oil, vapors and water are passed through a separating chamber, the water being removed from the bottom, the fixed gases from the top, and the oil from the upper layer of liquid, above the water.

The oil which is obtained by the method described above is the odorant which is the subject of the present invention. The oil from the separator may be neutralized as with caustic soda, if desired, washed with water, and passed to storage.

The odorant described hereinabove may be employed in any desired manner. For example, it may be introduced into the fuel gas in the form of a spray, although preferably the gas is passed through a tower or other porous bed of material exposing a large surface area over which the odorant is sprayed or held by the absorption of the material with which the tower is packed. In view of the relatively small quantities of odorant necessary to impart a distinctive odor to the gas,

the latter method, namely, addition to a column containing rocks,'bri'ck or tile, is preferred as more accurate control may be thus maintained over the quantity of odorant added to the gas.

We claim:

1. An odorant for gaseous fuels which lack distinctive odor, comprising a volatile oil having a distillation range of between F. and 600 F., said oil having a total sulphur content of above 2%, said oil being a fractional distillation product of the oil produced on decomposing acid sludge formed during treatment of sulphur hearing mineral oil with sulphuric acid for the removal of sulphur, said oil having a penetrating signal odor readily discernible in concentrations of about 0.25 part and more per million when mixed with a gaseous combustible hydrocarbon fuel, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a hetero-atom.

2. An odorant for a gaseous combustible hydrocarbon fuel which has no marked inherent odor,

said odorant comprising a volatile oil having a distillation range of between 100 F. and 420 F. and yielding not less than 70% by distillation at 340 F'., said oil having a total sulphur content of above 2% and said oil being a fractional distillation product of the oil resulting from the decomposition of acid sludge formed during treatment of sulphur bearing mineral oil with sulphuric acid for the removal of sulphur bodies, said oil having a penetrating signal odor readily discernible in concentrations of about 0.25 part and more per million, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a hetero-atom.

3. An odorant for a gaseous combustible hydrocarbon fuel having no marked inherent odor, said odorant comprising a volatile oil having a distillation range of between 100 F. and 420 F., said oil having a total sulphur content of above 2% and said oil being a fractional distillation product of the oil formed on decomposing acid sludge derived during treatment of sulphur bearing mineral oil with sulphuric acid for the removal of sulphur bodies, said oil having a penetrating signal odor readily discernible in concentrations of about 0.25 part and more per million, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a hetero-atom.

4. An odorant for a gaseous combustible hydrocarbon fuel having no marked inherent odor, said odorant comprising a volatile oil having a distillation range of between 100 F. and 600 F., said oil having a total sulphur content of between 2 and 18%, said oil being a fractional distillation product of oil formed from decomposition of acid sludge derived during the treatment of sulphur bearing mineral oil with sulphuric acid for the removal of sulphur bodies, said oil having a penetrating signal odor readily discernible in concentrations of about 0.25 part and more per million, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a heteroatom.

5. An odorant for a gaseous hydrocarbon fuel,

comprising a volatile oil having a distillation range of betWeenlOO" F. and 600 F., said oil having a total sulphur content of between 2 and 18% being substantially free from sulphur dioxide, said oil being a fractional distillation product of oil from the decomposition of acid sludge formed during the treatmentof sulphur bearing mineral oil with sulphuricv acid for the removal of sulphur bodies, said oil having a penetrating signal odor readily discernible in concentrations of about 0.25 part and more per million, the effective odorizing constituentsof the oil comprising. principally organic cyclic sulfides of the saturated ring heterr ocyclic type containing three or more carbon atoms and sulphur asia hetero-atom.

g 6. An odorant for a gaseous hydrocarbon fuel, said odorant comprising a volatile oil having a distillation, range of between 100 F. and-600 said oil having 'a total sulphur content of above 2% being-substantially free from sulphur dioxide, said oil beingafractional distillation product of oil obtained from the decomposition of acid sludge derived during treatment of sulphur bearingmineral oil withsulphuric acid for the 'removal of sulphur bodies, said oil having a penetrating signal odor readily discernible in concentrations of about 0.25 part and more per million, the effective odorizing constituents of the oil 1 comprising principally organic cyclic sulfides of the saturated ring heterocy'clic type containing three or more carbon atoms and 'sulphur'as a hetero-atom. I 1

v7. An odorant for gaseous fuel comprising a volatileoil having a distillation range of between 100" and 420 F. and yielding not less than 70% by distillation at 340 F., said oil having a total sulphur content of between 2 and 18% being substantially free from sulphur dioxide, said oil being a fractional distillation product of the oil obtained from the decomposition of acid sludge derived duringtreatment of sulphur bearing mineral oil with sulphuric acid for the removal of sulphur bodies,'said oil having a penetrating signal odor readily discernible, in concentrations of about 0.25 part and more per million, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a hetero-atom. 8. An odorant for a gaseous fuel, comprising a gaseous volatile oil having a distillation range of between 100 F. and 420 F., said oil having a totalsulphur content of between 2 and'l8% being substantially free of sulphur dioxide, said oil being a product of hydrolysis followed by fractionation of acid sludge formed during treatment of sulphur bearing mineral oil with sulphuric acid for the removal of sulphur bodies, said oil having a penetrating signal odor readily discernible in concentrations of about 0.25 part and more per million, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a hetero-atom.

- 9. An odorant for a gaseous fuel, comprising a volatile oil having a distillation range of behetero-atom.

tween 100 F. and 600 F., said oil having a total sulphur content of between 2 and 18% being substantially free from sulphur dioxide, said oil being a product of hydrolysis and fractionation of acid sludge formed'during treatment of sulphur bearing mineral oil with sulphuric acid for the removal of sulphur bodies, said oil having a penetrating signal odor readily discernible in concentrations of about 70.25 part, or more per million, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a 10. A process of producing an odorant for gaseous fuels, which process comprises subjecting the sulphuric acid sludge obtained from the sulphuric acid treatment of low boiling point petro--, leum oils to decomposition to separate therefrom an oil containing volatile cyclic sulphur bodies 'and' volatile organic compounds, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a hetero-atom, and subjecting said oil obtained from such decomposition to fractionation to separate therefrom ,a fraction having a boiling point range of between 100 F. and 420 F., and having a sulphur content of between 2 and 30%.

11. A process of producing an odorant for gaseous fuels, which'process comprises subjecting the sulphuric acid sludge obtained from the sulphuric acid treatment of low boiling point petroleum oils to decomposition to separate therefrom an oil containing volatile cyclic sulphur bodies 7 and volatile organic compounds, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a hetero-atom, fractionating such oil to separate therefrom a fraction having a boiling point range of between 100 F. and 420 F; and yielding not less than 70% by distillation at 340 F. and having a total sulphur content of between 2 and 18% and being substantially free from sulphur dioxide.

12. A process of producing an odorant for gaseous fuels, which process comprises subjecting the sulphur acid sludge obtained from the sulphuric acid treatment of low boiling point petroleum oils to hydrolysis to separate therefrom an oil containing volatile cyclic sulphur bodies and volatile organic compounds, the effective odorizing constituents of the oil comprising principally organic cyclic sulfides of the saturated ring heterocyclic type containing three or more carbon atoms and sulphur as a hetero-atom, subjecting the oils obtained from said hydrolysis to fractionation to separate therefrom a fraction having a boiling point range of between 100 Rand 600 F., said oil having a total sulphur content of between 2 and 18% and being substantially free of sulphur dioxide.

WILLIAM H. HAMPTON. JOHN T. RUTHERFORD. 

